Adhesive activation



Aug. l, i946.

F.V{NUGENT VADHESIVE ACTIVATION Filed Sept. 23, 1944 A 1M/eww? i:Frederick Vfulgen Patented Aug. 13, 1946 UNITED STATES PATENT OFFICEADHESIVE ACTIVATION Frederick V. Nugent, Abington, Mass., assigner to B.B. Chemical Co., Boston, Mass., a corporation of MassachusettsApplication September 23, 1944, Serial No. 555,579

2 Claims.

This invention relates to improvements in the joining together offibrous surfaces with cements or adhesives and more particularly to thejoining of shoe parts, such as leather soles to shoe uppers by means ofsynthetic rubber-like adhesives.

In the manufacture of shoes in which the soles are attached to theuppers by means of adhesives it is conventional practice to apply asuitable adhesive to the over-lasted edge of the shoe upper from onehour to eighteen hours before the attachment and to cement the marginalportion of the shoe sole from five hours to one week prior toattachment. The adhesive on the uppers and soles is therefore hard anddry when it becomes convenient to join the parts together. When theparts are to be assembled the dry and hardened adhesive on the sole isactivated or softened by a suitable solvent the volatility of which mustbe so adjusted as to allow the operator suiiicient time to assemble theparts before placing them in a pressure device. In the present practicefor temporarily restoring normal adhesiveness it is customary to applythe activator or softener by means of a brush and in so doing thequantity of the solvent or activator applied is so excessive that thesoles must be set aside for about an hour before they are applied to theshoe uppers, necessitating care in timing the operations of shoemanufacture and contributing to the uncertainty as to whether the cementis properly activated. If such delay preliminary to sole attachment isto be avoided, it is necessaryin alternative customary practice, for theshoes to remain in the pressure device for a considerable time to permitsubstantially complete removal of the volatile material in the softeneror until the adhesive has set completely. In other words, a considerabledelay has been heretofore essential in shoe manufacturing procedureeither before or after sole laying. Another diiculty that has arisen isthat when a machine is used to apply the activator or solvent to themargin of the soles the operator may not notice that the supply ofsolvent has given out or is irregular with the result that theattachment of the sole to the upper Vis neither secure nor reliable. Y

t .One object of this invention is the provision of an improved methodof joining fibrous surfaces together with synthetic rubber-like adhesivecement previously applied to the surfaces and allowed to dry in whichmethod no undue delay or interruption in manufacturing procedure need beencountered,

A further object of the invention is to provide that a cemented portionhas been activated or softened prior to its assembly or joinder withanother cemented part. l

The invention will be explained with reference to the accompanyingdrawing, in which Fig. 1 shows a perspective view of a shoe sole showingthe marginal portion to which adhesive cement has been applied forattaching the sole to a shoe; and

Fig. 2 shows an elevation view of the main pory tion of a machineadapted to carry out the method of this invention.

I have discovered that by applying an activator or solvent lightly tohardened synthetic rubberlike adhesive cement by spraying, the cement istemporarily restored to attaching condition substantially immediately,that is to say, no waiting is required between the activation of thecement and the sole attaching operation (for example) even with ordinaryactivators such as toluene. When spraying is used it is possible toactivate merely the surface of the cement and no excess solvent need bedissipated ,before the parts are ready for attachment. Ithas been foundthat in spray activation of neoprene or polymerized chloroprene cement,for example, an initial bond strength of 15 to 20 pounds may be obtainedas compared with the five-pound bond ordinarily obtained with liquidsolvent activation. The neoprene or chloroprene cement spoken of is ofthe type as described in United ,States Letters Patent No. 2,061,296,granted November 17, 1936, on an application filed in the name of W. H.Wedger'. By initial bond is meant the strength l tested immediatelyafter a time dwell in an at- Similar copolymers may also be obtainedcommercially under the trade name Chemigum manufactured by Goodyear'Iire and Rubber Company, Akron, Ohio, or under the trade name Perbunanmanufactured by the Standard Oil a method for clearly indicating bymeans of color Company of New Jersey. For butadiene-acrylonitrile typecements, suitable illustrative solvents for application by spray areacetone and methyl ethyl ketone. With the use of any of these cementsspray activation necessitates prompt joinder of the parts, that is, aperiod not in excess preferable that they be maintained under soleattaching pressure for at least 40 to 60 seconds, and this may beaccomplished conveniently in a machine such as shown in UnitedStatesLetters Patent No. 2,047,185, granted July 14, 1936, on an applicationfiled in the namev of Milton H. Ballard et al.

When it is desired that a sole be molded or..V

formed the cement coated sole is mulled or tem'- pered and shaped. If larelatively long period of time elapses between the sole forming ormolding and the sole attaching operations the-sole may be brought againinto temper just prior to the sole attaching operation. Before theapplication of an activator or softener to the sole, Whether or not thesole is formed or molded, the sole is preferably mulled or tempered inorder to make the same more iiexible, and to reduce the tendency of thesole to pull away 'from the upper after the release of thescle-attaching pressure. The step of activation is not adverselyaffected by the prior tempering operation.

I have avoided uncertainties in the prior methods of activation, whethersuch methods be by brush or spray application of a solvent, by'incorporating a color indicator in the activator or solvent. A smallquantity of a substance is placed in the activator, which substance willreact with an' ingredient such as a ller in the cement and therebyconstitute a color indication of4 the cement activation. The use of acolor indicator enables an operatorl by casual Vobservation to observeimmediately whether or not a hardened cement'lias been activated andVjhe can therefore proceed immediately to carry out the attaching step(if spray activation is used) or can proceed with his timing `(if brushactivation isV used) and with greater certainty of result.

The use of the color indicator of this invention is especially andpeculiarly adapted for combination with the spray activation feature'forthe reason that spray activation requires vsuch a small amount ofactivator or solvent that an indicator isV particularly advantageous toWarn an operator from proceeding'with cement attaching Without properactivation.

It is customary in the use of adhesive lcements to incorporate therewitha quantity of magnesium oxide which usually functions as a filler. Intheuse of such cements l have found it` aolvantageousto use an activatorcontaining a small quantity of symmetrical diphenyl carbazone (CeHaN-N-CO -NH -NH' Cel-lla) Approximately three grams of this material is usedper gallon of solvent when activation is by means of a spray.Approximately one gram per gallon of solvent is used for brushactivation. A suitable solvent composition With a color indicator forthe activation has been found to be as follows:

ASixrounces Denatured alcohol Six ounces 1 Ethyl acetate One or threegrams Diphenyl carbazide Dilute to one gallon with toluene. Thissolution 'should be'subjected to -agingfor five days; the aging resultsin the oxidation of the carbazide to carbazone. The necessity for agingmay be obviated by dissolving diphenyl carbazide in toluene andoxidizing the carbazide to carbazone by means of quinone. The formulafor symmetrical diphenyl carbazide is as follows:(CsHsNH-NH-CO-NH-NH-CsHs). The indicator as dissolved in the solventpresents a bright red color but when this is sprayed on an Auncoatedshoe sole it is practically invisible. Wherever the indicator contacts ahardened cement which includes magnesium oxide there is an instantaneouschemical reaction which imparts a distinct red color to the cement. Thisvcolor 'fades ina few days if the parts are not attached together bymeans of the cement. Use 'of the. indicator inthe activator does nothinder reactivation of the cement at a later date. In employing anindicator as set forth in this in- Vention it is necessary to omit anyaccelerators of curing from the activator because such acceleratorswould react with the cli-phenyl carbazone. The use of such indicator isgreatly superior to the use of dyes as dyes tend to migrate and are aptto discolor the objects treated, such as the uppers or soles of shoes.There is no migration or discoloration in the use of diphenyl carbazone.

In carrying out the method a shoe, to which a sole is `to be applied,may have its upper llasted over its insole in any usual manner. YForexample, the heel seat portion may be lasted `with tacks and at theshank portion the upper may be Worked over the last and secured inposition with staples by means of a machine such as the staple lastingmachine disclosed in Letters Pat ent of the United States No. 1,815,295,granted J uly 21, 1931, on an application led in the name of GeorgeGoddu. The Iforepart may be similarly lasted or the upper may be held inlasted position by cement alone. The overlasted margin of the upper ispreferably roughened before synthetic rubber-like adhesive cement isapplied thereto by hand or byv means of a cement applying machine suchas disclosed in Letters Patent No. 2,100,341, granted November 30, 1937,on an application filed in the name of Wilbur L. Mac- Kenzie. i

An outsole llll is prepared as shown in Fig. 1, the marginal portion ofits inner -face being roughened at I2 for the receptiony of syntheticrubber-like cement which is shown `as having been applied to the margin.The roughing may be done by any of the usual roughing machines employedin themanufacture of cemented shoes. The, cement may be applied to theoutsole by hand but preferably bya'machine such 'as disclosed in LettersPatent of the United States No. 2,042,479, granted June 2, 1936, on anapplication led in the name of Carl A. Newhall.

After the outsole and shoe -have been coated with adhesive cement theyare aliowed'to dry in the-customary manner and the outsole may then bemulled and formed before the use of a softener' or-activator for thecement.

The application of the softener `or activator may be done by a spray gunmounted in place of a brush- Von a coating applying machine as disclosedinlLetters Patent of the United States No. 2,073,647 granted March 15,1937, on an application filed-in the name of Carl A. Newhall. Thesubstitution of a spray gun on such a machine is shown in Fig. 2 inwhich a spray gun 20 is shown mountedat an angle to the horizontal onan-arm 22 extending from `the machine frame and'inposition to direct alight spray of activator material on the margin of the outsole as theoutsole is manipulated between the upper and lower feed rolls 24 and 26,Customary air and liquid feed connections 3l and 33 are shown. The spraygun is so adjusted that there is a ow of approximately four-tenths ofone cubic centimeter of the activator to each sole. The spray may easilybe maintained light by adjusting the gun to retain a large volume of airas compared with the amount of activator. 'Ihe trigger 30 of the spraygun may be operated by connecting it through arm 32 to the horizontaland sectional rod 34 which is rotated by the rod and lever system 36upon depression of a foot treadle (not shown) to which a vertical rod 38is attached. The feeding of an outsole and application of an activatorto the outsole during feeding are both under the control of the treadle.

The activating medium preferably includes a` small quantity of diphenylcarbazone and in such case the cement on the outsole is a cementcontaining a quantity of magnesium oxide.

Prcmptly after activation of the outsole cement (preferably evidenced bythe color produced in the cement), the outsole and shoe bottom arebrought into juXtaposition and under attaching pressure in a soleattaching machine of a type before referred to. The pressure ismaintained for 50 seconds and then the shoe may be removed from themachine as the strength of the initial bond is suiciently great to bereliable even though the last be immediately pulled from the shoe.

Having described my invention, what I claim `the United States is:

l. In the art of adhering fibrous materials together, that improvementwhich comprises adding a filler material yto a synthetic rubber-likeadhesive, applying the adhesive to areas of the parts to be joined andpermitting the adhesive to harden, providing a solvent activator forsaid adhesive and adding thereto an agent capable of subsequent reactionwith said filler material for producing a color, applying the agentcarrying activator to the hardened adhesive on at least one of saidareas to render the adhesive tacky and with a resulting reaction betweenthe agent and the filler giving a visual indication of the condition ofthe adhesive, and thereafter pressing the parts together to effect anadhesive bond.

2. In the art of adhering brous materials together, that improvementwhich comprises adding magnesium oxide to a synthetic rubber-likeadhesive, applying the adhesive to areas of the parts to be joined andpermitting the adhesive to harden, providing a solvent activatorsolution for said adhesive, said solution containing diphenyl carbazone,lightly spraying the said activator solution on the hardened adhesive ofat least one of said areas to render the adhesive tacky and with aresulting Vreaction between the diphenyl carbazone and the magnesiumoxide giving a visual indication of the condition of the adhesive, andthereafter pressing the parts together to effect an adhesive bond.

FREDERICK V. NUGENT.

